A rescue team inspects flooded areas after the passing of Hurricane Irma in Fajardo, Puerto Rico. (Photo by Jose Jimenez/Getty Images)

SAN JUAN, Puerto Rico (AP) - French, British and Dutch military authorities rushed aid to a devastated string of Caribbean islands Thursday after Hurricane Irma left at least 11 people dead and thousands homeless as it spun toward Florida for what could be a catastrophic blow this weekend.

Warships and planes were dispatched with food, water and troops after the fearsome Category 5 storm smashed homes, schools and roads, laying waste to some of the world's most beautiful and exclusive tourist destinations.

Hundreds of miles to the west, Florida braced for the onslaught, with forecasters warning that Irma could slam headlong into the Miami metropolitan area of 6 million people, punish the entire length of the state's Atlantic coast and move into Georgia and South Carolina.

More than a half-million people in Miami-Dade County were ordered to leave as Irma closed in with winds of 175 mph (281 kph).

"Take it seriously, because this is the real deal," said Maj. Jeremy DeHart, a U.S. Air Force Reserve weather officer who flew through the eye of Irma at 10,000 feet.

The hurricane was still north of the Dominican Republic and Haiti on Thursday evening, sweeping the neighboring nations on Hispaniola island with high winds and rain while battering the Turks and Caico islands on its other side.

Big waves smashed a dozen homes into rubble in the Dominican fishing community of Nagua, but work crews said all the residents had left before the storm. Officials said 11,200 people in all had evacuated vulnerable areas, while 55,000 soldiers had been deployed to help the cleanup.

In Haiti, two people were injured by a falling tree, a national roadway was blocked by debris and roofs were torn from houses along the northern coast but there were no immediate reports of deaths. Officials warned that could change as Irma continued to lash Haiti, where deforested hillsides are prone to devastating mudslides that have wiped out entire neighborhoods of precariously built homes in flood zones.

"We are vulnerable. We don't have any equipment to help the population," Josue Alusma, mayor of the northern city of Port de Paix, said on Radio Zenith FM.

About a million people were without power in Puerto Rico after Irma sideswiped the island overnight, and nearly half the territory's hospitals were relying on generators. No injuries were reported.

The first islands hit by the storm were scenes of terrible destruction.

French Prime Minister Edouard Philippe said four people were confirmed dead and about 50 injured on the French side of St. Martin, an island split between Dutch and French control. The toll could rise because rescue teams had yet to get a complete look at the damage.

At least four people were killed in the U.S. Virgin Islands, and officials said they expected to find more bodies. Authorities described the damage as catastrophic and said crews were struggling to reopen roads and restore power.

Three more deaths were reported on the British island of Anguilla, independent Barbuda and the Dutch side of St. Martin.

Irma also slammed the French island of St. Barts, tearing off roofs and knocking out electricity.

French Interior Minister Gerard Collomb said 100,000 food rations were sent to St. Barts and St. Martin, the equivalent of four days of supplies.

"It's a tragedy. We'll need to rebuild both islands," he said. "Most of the schools have been destroyed."

Photos and video of St. Martin circulating on social media showed major damage to the Philipsburg airport and heavy flooding in the coastal village of Marigot.

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"There is no power, no gasoline, no running water. Houses are under water, cars are floating through the streets, inhabitants are sitting in the dark in ruined houses and are cut off from the outside world," he said.

In the U.S. Virgin Islands, Gov. Kenneth Mapp said the U.S. military was sending troops to aid relief efforts.

The primary focus for now is "making sure people have meals, water and shelter," Mapp said. "An event of this magnitude is very chilling."

The territory's two islands were battered by 150 mph (241 kph) winds for four hours. Two fire stations, two fire police stations and the hospital on St. Thomas were destroyed. A curfew was ordered for St. John and St. Thomas that also covered about 5,000 tourists who were unable to leave before the storm.

Farther out in the Atlantic, Hurricane Jose strengthened into a Category 3 storm with 120 mph (195 kph) winds and posed a potential threat for Saturday to some of the same islands ravaged by Irma.

Irma, the most potent Atlantic Ocean hurricane ever recorded, appeared increasingly likely to rip into heavily populated South Florida on Sunday afternoon after threatening parts of the Turks and Caicos and the Bahamas on Thursday night and Friday and sweeping along Cuba's northern coast on Saturday.

People in Florida rushed to board up their homes, take their boats out of the water and gas up their cars. With gasoline running out and tensions rising, the Florida Highway Patrol escorted tanker trucks sent to replenish gas stations.

"It is wider than our entire state and could cause major and life-threatening impacts from coast to coast. Regardless of which coast you live on, be prepared to evacuate," Gov. Rick Scott said.

Brian McNoldy, a hurricane researcher at the University of Miami, said Irma could easily prove to be the costliest storm in U.S. history.

French President Emmanuel Macron's office said he would go to the islands as soon as the weather permits it. Saying he was "grief-stricken," Macron called for concerted efforts to tackle global warming to prevent similar natural disasters.

Two Dutch navy ships were in St. Martin with vital supplies. And two Dutch military aircraft were being sent the island of Curacao and on to St. Martin to deliver food and water intended to last the population of 40,000 five days. The aircraft were carrying 100 extra troops to deliver aid, repair infrastructure and restore order.

Britain was sending hundreds of troops and the Royal Navy flagship HMS Ocean to Anguilla, Montserrat and the British Virgin Islands.

In Anguilla, officials reported extensive damage to the airport, hospitals, shelters and schools and said 90 percent of roads were impassable.

On Barbuda, nearly every building was damaged when the hurricane's core crossed almost directly over the island early Wednesday. About 60 percent of its roughly 1,400 residents were left homeless, Antigua and Barbuda Prime Minister Gaston Browne said.

He said roads and telecommunications systems were wrecked and recovery will take months, if not years.